U.S. patent application number 15/112417 was filed with the patent office on 2017-02-02 for method for manufacturing a strip having a variable thickness and associated strip.
This patent application is currently assigned to APERAM. The applicant listed for this patent is APERAM. Invention is credited to Nicolas Laurain, Roland Panier, Pierre-Louis Reydet.
Application Number | 20170029918 15/112417 |
Document ID | / |
Family ID | 50070644 |
Filed Date | 2017-02-02 |
United States Patent
Application |
20170029918 |
Kind Code |
A1 |
Panier; Roland ; et
al. |
February 2, 2017 |
METHOD FOR MANUFACTURING A STRIP HAVING A VARIABLE THICKNESS AND
ASSOCIATED STRIP
Abstract
A method for manufacturing a strip having a variable thickness
along its length, comprising the steps: an initial strip of
constant thickness is provided; homogeneous cold rolling of the
initial strip along its length in order to obtain an intermediate
strip of constant thickness along the rolling direction; flexible
cold rolling of the intermediate strip along its length in order to
obtain a variable thickness strip, having, along its length, first
areas with a first thickness (e+s) and second areas with a second
thickness (e), less than the first thickness (e+s), continuous
annealing of the strip. The plastic deformation ratio generated,
after an optional intermediate recrystallization annealing, by the
homogeneous cold rolling and the flexible cold rolling steps in the
first areas is greater than or equal to 30%.
Inventors: |
Panier; Roland; (NEVERS,
FR) ; Reydet; Pierre-Louis; (URZY, FR) ;
Laurain; Nicolas; (BRIIS-SOUS-FORGES, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
APERAM |
Luxembourg |
|
LU |
|
|
Assignee: |
APERAM
Luembourg
LU
|
Family ID: |
50070644 |
Appl. No.: |
15/112417 |
Filed: |
January 17, 2014 |
PCT Filed: |
January 17, 2014 |
PCT NO: |
PCT/IB2014/058350 |
371 Date: |
October 11, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C21D 1/42 20130101; B21C
37/065 20130101; C22C 38/105 20130101; Y02P 10/253 20151101; B23K
31/02 20130101; C21D 8/0273 20130101; F16L 9/17 20130101; C22C
38/14 20130101; Y02P 10/25 20151101; C21D 9/52 20130101; C22C
19/058 20130101; C22C 38/40 20130101; C22C 38/08 20130101; C22C
19/03 20130101; C22C 38/52 20130101; C21D 8/0226 20130101; C21D
6/001 20130101; C22C 38/04 20130101; C22C 38/50 20130101; B23K
31/027 20130101; C22F 1/10 20130101; C22C 38/02 20130101; B21B
2261/043 20130101; B23K 2101/06 20180801; B21B 17/02 20130101; C22C
19/005 20130101; C21D 8/0268 20130101; B23K 2101/185 20180801; B23K
2103/04 20180801; C21D 1/38 20130101; C22C 30/00 20130101; C21D
8/0236 20130101 |
International
Class: |
C21D 9/52 20060101
C21D009/52; C22C 38/50 20060101 C22C038/50; C22C 38/40 20060101
C22C038/40; C22C 38/04 20060101 C22C038/04; C22C 38/02 20060101
C22C038/02; B21B 17/02 20060101 B21B017/02; C21D 1/42 20060101
C21D001/42; C21D 1/38 20060101 C21D001/38; B23K 31/02 20060101
B23K031/02; C22C 30/00 20060101 C22C030/00; C22C 19/05 20060101
C22C019/05; C22C 38/52 20060101 C22C038/52; C21D 8/02 20060101
C21D008/02 |
Claims
1. A method for manufacturing a strip having a variable thickness
along its length, made of an iron-based alloy, the strip being made
of an alloy comprising by weight: 34.5%.ltoreq.Ni.ltoreq.53.5%
0.15%.ltoreq.Mn.ltoreq.1.5% 0.ltoreq.Si.ltoreq.0.35%
0.ltoreq.C.ltoreq.0.07% optionally: 0.ltoreq.Co.ltoreq.20%
0.ltoreq.Ti.ltoreq.0.5% 0.01%.ltoreq.Cr.ltoreq.0.5% the remainder
being iron and impurities necessarily resulting from the
elaboration, the method successively comprising the following
steps: providing an initial strip of constant thickness (E.sub.0),
obtained by hot rolling; homogeneous cold rolling of the initial
strip along its length in order to obtain an intermediate strip of
constant thickness (E.sub.c) along the rolling direction; flexible
cold rolling of the intermediate strip along its length in order to
obtain a strip of variable thickness along the rolling direction,
the variable thickness strip having along its length, first areas
having a first thickness (e+s) and second areas (10) having a
second thickness (e), smaller than the first thickness (e+s),
continuous final annealing of the variable thickness strip in a
final annealing oven, wherein the plastic deformation ratio
generated, after an optional intermediate recrystallization
annealing, by the steps of homogeneous cold rolling and of flexible
cold rolling in the first areas of the variable thickness strip is
greater than or equal to 30% and in which the difference
(.DELTA..tau.) between the plastic deformation ratio (.tau..sub.2)
generated, after an optional intermediate recrystallization
annealing, by the steps of homogeneous cold rolling and of flexible
cold rolling in the second areas and the plastic deformation ratio
generated, after an optional intermediate recrystallization
annealing, by the steps of homogeneous cold rolling and of flexible
cold rolling in the first areas of the variable thickness strip is
smaller than or equal to 13% if the thickness (E.sub.0) of the
initial strip is strictly greater than 2 mm and smaller than or
equal to 10% if the thickness (E.sub.0) of the initial strip is
smaller than or equal to 2 mm.
2. The manufacturing method according to claim 1, wherein the final
recrystallization annealing is carried out at a final annealing
temperature comprised between 850.degree. C. and 1200.degree. C.
and a dwelling time in the final annealing oven comprised between
20 seconds and 5 minutes.
3. The manufacturing method according to claim 1, wherein the
homogeneous rolling step comprises at least one intermediate
recrystallization annealing carried out between two successive
homogeneous rolling passes and/or at the end of the homogeneous
rolling before flexible cold rolling of the intermediate strip.
4. The manufacturing method according to claim 3, wherein the
intermediate recrystallization annealing is a continuous annealing
carried out in an intermediate annealing oven with a temperature of
the strip during intermediate annealing comprised between
850.degree. C. and 1200.degree. C. and a dwelling time in the
intermediate annealing oven comprised between 30 seconds and 5
minutes.
5. The manufacturing method according to claim 1, wherein the
thickness (E.sub.c) of the intermediate strip is equal to the
second thickness (e) multiplied by a reduction coefficient
comprised between 1.05 and 1.5.
6. The manufacturing method according to claim 1, wherein the first
thickness (e+s) is equal to the second thickness (e) multiplied by
a multiplication coefficient comprised between 1.05 and 1.5.
7. The manufacturing method according to claim 1, wherein before
the homogeneous cold rolling step, the initial strip undergoes a
microstructure homogenization annealing, in particular a continuous
annealing, in a microstructure homogenization annealing oven with a
dwelling time in the microstructure homogenization annealing oven
comprised between 2 minutes and 25 minutes and a temperature of the
microstructure homogenization annealing oven comprised between
850.degree. C. and 1200.degree. C.
8. The manufacturing method according to claim 1, wherein the
initial strip is obtained from a semi-finished product such as a
slab or an ingot consisting of an alloy elaborated in an electric
arc oven or a vacuum induction oven.
9. The manufacturing method according to claim 1, wherein the
thickness (E.sub.0) of the initial strip is comprised between 1.9
mm and 18 mm.
10. The manufacturing method according to claim 1, which comprises,
after the final recrystallization annealing step, a step for
leveling the variable thickness strip.
11. The manufacturing method according to claim 1, wherein the
alloy comprises by weight: 34.5%.ltoreq.Ni.ltoreq.42.5%
0.15%.ltoreq.Mn.ltoreq.0.5% 0.ltoreq.Si.ltoreq.0.35%
0.010%.ltoreq.C.ltoreq.0.050% optionally: 0.ltoreq.Co.ltoreq.20%
0.ltoreq.Ti.ltoreq.0.5% 0.01%.ltoreq.Cr.ltoreq.0.5% the remainder
being iron and impurities necessarily resulting from the
elaboration.
12. A method for manufacturing at least one blank, comprising:
carrying out the manufacturing method according to claim 1, so as
to obtain a strip having a variable thickness along its length; and
cutting the variable thickness strip so as to obtain several
blanks.
13. The method according to claim 12, wherein the cutting of the
variable thickness strip is carried out in the first areas, each
blank being formed of a portion of the variable thickness strip
located between two successive first areas.
14. A method for manufacturing a cryogenic tube segment,
comprising: manufacturing at least one blank by carrying out the
manufacturing method according to claim 13, the blank comprising
longitudinal edges extending along the length of the blank; and
then rolling up the blank along its width; and welding together the
longitudinal edges of the rolled up blank in order to form a tube
segment.
15. A variable thickness strip which may be obtained by the
manufacturing method according to claim 1, the variable thickness
strip having, along its length, first areas having a first
thickness (e+s) and second areas having a second thickness (e)
smaller than the first thickness (e+s), the variable thickness
strip being made of an alloy comprising by weight:
34.5%.ltoreq.Ni.ltoreq.53.5% 0.15%.ltoreq.Mn.ltoreq.1.5%
0.ltoreq.Si.ltoreq.0.35% 0.ltoreq.C.ltoreq.0.07% optionally:
0.ltoreq.Co.ltoreq.20% 0.ltoreq.Ti.ltoreq.0.5%
0.01%.ltoreq.Cr.ltoreq.0.5% the remainder being iron and impurities
necessarily resulting from the elaboration.
16. The strip according to claim 15, the first areas having a first
average grain size (G1.sub.ASTM) and the second areas having a
second average grain size (G2.sub.ASTM), the absolute value
difference between the first grain size (G1.sub.ASTM) and the
second grain size (G2.sub.ASTM) being less than or equal to 0.5
numbers according to the ASTM E112-10 standard.
17. The strip according to claim 15, the alloy comprising by
weight: 34.5.ltoreq.Ni.ltoreq.42.5% 0.15%.ltoreq.Mn.ltoreq.0.5%
0.1%.ltoreq.Si.ltoreq.0.35% 0.010%.ltoreq.C.ltoreq.0.050%
optionally: 0.ltoreq.Co.ltoreq.20% 0.ltoreq.Ti.ltoreq.0.5%
0.01%.ltoreq.Cr.ltoreq.0.5% the remainder being iron and impurities
necessarily resulting from the elaboration.
18. A blank which may be obtained by the method of claim 12, the
blank having, along its length, at least one first reinforced area
having a first thickness (e+s) and at least one second area having
a second thickness (e) smaller than the first thickness (e+s), the
blank being made of an alloy comprising by weight:
34.5%.ltoreq.Ni.ltoreq.53.5% 0.15%.ltoreq.Mn.ltoreq.1.5%
0.ltoreq.Si.ltoreq.0.35% 0.ltoreq.C.ltoreq.0.07% optionally:
0.ltoreq.Co.ltoreq.20% 0.ltoreq.Ti.ltoreq.0.5%
0.01%.ltoreq.Cr.ltoreq.0.5% the remainder being iron and impurities
necessarily resulting from the elaboration.
19. The blank according to claim 18, the first reinforced area
having a first average grain size (G1.sub.ASTM) and the second area
having a second average grain size (G2.sub.ASTM), the absolute
value difference between the first grain size (G1.sub.ASTM) and the
second grain size (G2.sub.ASTM) being less than or equal to 0.5
numbers according to the ASTM E112-10 standard.
20. The blank according to claim 18, the alloy comprising by
weight: 34.5.ltoreq.Ni.ltoreq.42.5% 0.15%.ltoreq.Mn.ltoreq.0.5%
0.1%.ltoreq.Si.ltoreq.0.35% 0.010%.ltoreq.C.ltoreq.0.050%
optionally: 0.ltoreq.Co.ltoreq.20% 0.ltoreq.Ti.ltoreq.0.5%
0.01%.ltoreq.Cr.ltoreq.0.5% the remainder being iron and impurities
necessarily resulting from the elaboration.
21. A tube segment which may be obtained by the method according to
claim 14, which is made of an alloy comprising by weight:
34.5%.ltoreq.Ni.ltoreq.53.5% 0.15%.ltoreq.Mn.ltoreq.1.5%
0.ltoreq.Si.ltoreq.0.35% 0.ltoreq.C.ltoreq.0.07% optionally:
0.ltoreq.Co.ltoreq.20% 0.ltoreq.Ti.ltoreq.0.5%
0.01%.ltoreq.Cr.ltoreq.0.5% the remainder being iron and impurities
necessarily resulting from the elaboration, and which segment
comprises a cylindrical central area having a thickness (e)
surrounded by cylindrical reinforced ends formed in one piece with
the central area having a thickness greater than the thickness (e)
of the central area.
22. The tube segment according to claim 21, wherein the alloy
comprises by weight: 34.5.ltoreq.Ni.ltoreq.42.5%
0.15%.ltoreq.Mn.ltoreq.0.5% 0.1%.ltoreq.Si.ltoreq.0.35%
0.010%.ltoreq.C.ltoreq.0.050% optionally: 0.ltoreq.Co.ltoreq.20%
0.ltoreq.Ti.ltoreq.0.5% 0.01%.ltoreq.Cr.ltoreq.0.5% the remainder
being iron and impurities necessarily resulting from the
elaboration.
23. An assembly comprising at least one blank according to claim 18
and a part welded to the blank.
24. The assembly according to claim 23, wherein the part is welded
to the first reinforced area of the blank.
25. (canceled)
26. The method according to claim 1, wherein
0.1%.ltoreq.Si.ltoreq.0.35%.
27. The method according to claim 2, wherein the dwelling time in
the final annealing oven comprised between 30 seconds and 3
minutes.
28. The method according to claim 11, wherein
0.1%.ltoreq.Si.ltoreq.0.35%.
29. The variable thickness strip according to claim 15, wherein
0.1%.ltoreq.Si.ltoreq.0.35%.
30. The blank according to claim 18, wherein
0.1%.ltoreq.Si.ltoreq.0.35%.
31. The tube segment according to claim 21, wherein
0.1%.ltoreq.Si.ltoreq.0.35%.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is the U.S. National Phase under 35 U.S.C.
.sctn.371 of International Application PCT/IB2014/058350, filed
Jan. 17, 2014, which are hereby incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for manufacturing
a strip with variable thickness along its length, made of an
iron-based alloy.
BACKGROUND OF THE INVENTION
[0003] Cryogenic Invar.RTM., notably Invar.RTM. M93, are alloys
which have low thermal expansion coefficients, which makes them
notably attractive for transporting cryogenic fluids.
[0004] In such applications, elements made of cryogenic Invar.RTM.
of different thicknesses may be assembled, for example by
welding.
[0005] The thereby obtained assemblies do not give entire
satisfaction. Indeed, the welds form weakened areas of the
structures formed by the assembled elements. The presence of these
weakened areas may result in a reduction of the fatigue
strength.
SUMMARY OF THE INVENTION
[0006] An object of the invention is to solve this problem by
proposing a method for manufacturing a strip mainly based on iron
and nickel which gives the possibility of producing structures that
are reinforced from a mechanical point of view.
[0007] For this purpose, the invention relates to a manufacturing
method.
[0008] According to particular embodiments, the manufacturing
method has one or several of the characteristics, which are taken
individually or according to all the technically possible
combinations.
[0009] The invention also relates to a method for manufacturing a
blank.
[0010] The invention also relates to a method for manufacturing a
cryogenic tube segment.
[0011] The invention also relates to a variable thickness
strip.
[0012] The invention also relates to a blank.
[0013] The invention also relates to a cryogenic tube segment.
[0014] The invention also relates to an assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The invention will be better understood upon reading the
description which follows, only given as an example, and made with
reference to the appended drawings, wherein:
[0016] FIG. 1 is a schematic longitudinal sectional view of an
initial strip;
[0017] FIG. 2 is a schematic longitudinal sectional view of an
intermediate strip;
[0018] FIG. 3 is a schematic longitudinal sectional view of a
variable thickness strip;
[0019] FIG. 4 is a schematic illustration of a blank obtained by
the manufacturing method according to the invention;
[0020] FIG. 5 is a schematic longitudinal sectional illustration of
a first assembly of a blank with a second part;
[0021] FIG. 6 is a schematic longitudinal sectional illustration of
two blanks assembled end to end; and
[0022] FIG. 7 is a schematic sectional illustration of a cryogenic
tube.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] An exemplary method for manufacturing a strip having a
variable thickness along its length made of an alloy mainly based
on iron and nickel according to the invention will now be
described.
[0024] In a first step of this method, an initial strip 1 obtained
by hot rolling is provided.
[0025] The initial strip 1 is a strip made of an alloy of the
cryogenic Invar type. This alloy comprises by weight:
[0026] 34.5%.ltoreq.Ni.ltoreq.53.5%
[0027] 0.15%.ltoreq.Mn.ltoreq.1.5%
[0028] 0.ltoreq.Si.ltoreq.0.35%, preferably
0.1%.ltoreq.Si.ltoreq.0.35%
[0029] 0.ltoreq.C.ltoreq.0.07%
[0030] optionally:
[0031] 0.ltoreq.Co.ltoreq.20%
[0032] 0.ltoreq.Ti.ltoreq.0.5%
[0033] 0.01%.ltoreq.Cr.ltoreq.0.5%
[0034] the remainder being iron and impurities necessarily
resulting from the elaboration.
[0035] The silicon notably has the function of allowing deoxidation
and of improving the corrosion resistance of the alloy.
[0036] An alloy of the cryogenic Inver type is an alloy which has
three main properties:
[0037] It is stable towards the martensitic transformation until
below the liquefaction temperature T.sub.L of a cryogenic fluid.
This cryogenic fluid is for example liquid butane, propane,
methane, nitrogen or oxygen. The contents of gammagenic elements,
nickel (Ni), manganese (Mn) and carbon (C), of the alloy are
adjusted so that the onset temperature of the martensitic
transformation is strictly less than the liquefaction temperature
T.sub.L of the cryogenic fluid.
[0038] It has a low average thermal expansion coefficient between
room temperature and the liquefaction temperature T.sub.L of the
cryogenic fluid.
[0039] It does not exhibit any "ductile-fragile" resilience
transition.
[0040] The alloy used preferably has:
[0041] an average thermal expansion coefficient between 20.degree.
C. and 100.degree. C. of less than or equal to 10.5.times.10.sup.-6
K.sup.-1, in particular less than or equal to 2.5.times.10.sup.-6
K.sup.-1;
[0042] an average thermal expansion coefficient between
-180.degree. C. and 0.degree. C. of less than or equal to
10.times.10.sup.-6 K.sup.-1, in particular less than or equal to
2.times.10.sup.-6 K.sup.-1; and
[0043] a resilience greater than or equal to 100 joule/cm.sup.2, in
particular greater than or equal to 150 joule/cm.sup.2, at a
temperature greater than or equal to -196.degree. C.
[0044] Preferably, the alloy used has the following composition, in
weight %:
[0045] 34.5.ltoreq.Ni.ltoreq.42.5%
[0046] 0.15%.ltoreq.Mn.ltoreq.0.5%
[0047] 0.ltoreq.Si.ltoreq.0.35%, preferably
0.1%.ltoreq.Si.ltoreq.0.35%
[0048] 0.010%.ltoreq.C.ltoreq.0.050%
[0049] optionally:
[0050] 0.ltoreq.Co.ltoreq.20%
[0051] 0.ltoreq.Ti.ltoreq.0.5%
[0052] 0.01%.ltoreq.Cr.ltoreq.0.5%
[0053] the remainder being iron and impurities necessarily
resulting from the elaboration.
[0054] In this case, the alloy used preferably has:
[0055] an average thermal expansion coefficient between 20.degree.
C. and 100.degree. C. of less than or equal to 5.5.times.10.sup.-6
K.sup.-1;
[0056] an average thermal expansion coefficient between
-180.degree. C. and 0.degree. C. of less than or equal to
5.times.10.sup.-6 K.sup.-1; and
[0057] a resilience greater than or equal to 100 joule/cm.sup.2, in
particular greater than or equal to 150 joule/cm.sup.2, at a
temperature greater than or equal to -196.degree. C.
[0058] Still more particularly,
[0059] 35%.ltoreq.Ni.ltoreq.36.5%
[0060] 0.2%.ltoreq.Mn.ltoreq.0.4%
[0061] 0.02.ltoreq.C.ltoreq.0.04%
[0062] 0.15.ltoreq.Si.ltoreq.0.25%
[0063] optionally
[0064] 0.ltoreq.Co.ltoreq.20%
[0065] 0.ltoreq.Ti.ltoreq.0.5%
[0066] 0.01%.ltoreq.Cr.ltoreq.0.5%
[0067] the remainder being iron and impurities necessarily
resulting from the elaboration.
[0068] In this case, the alloy preferably has:
[0069] an average thermal expansion coefficient between 20.degree.
C. and 100.degree. C. of less than or equal to 1.5.times.10.sup.-6
K.sup.-1;
[0070] an average thermal expansion coefficient between
-180.degree. C. and 0.degree. C. of less than or equal to
2.times.10.sup.-6 K.sup.-1;
[0071] a resilience greater than or equal to 200 joule/cm.sup.2 at
a temperature greater than or equal to -196.degree. C.
[0072] Such an alloy is an alloy of the cryogenic Invar.RTM. type.
The trade name of this alloy is Invar.RTM.-M93.
[0073] Conventionally, the alloys used are elaborated in an
electric arc furnace or an induction vacuum furnace.
[0074] After operations of refining in a ladle, which allow
adjusting the contents of residual alloy elements, the alloys are
cast as semi-finished products, which are subjected to hot
processing, in particular by hot rolling, in order to obtain
strips.
[0075] These semi-finished products are for example ingots.
Alternatively, they are formed by slabs continuously cast by means
of an installation for continuous casting of slabs.
[0076] The thereby obtained strip is stripped and polished in a
continuous process in order to limit its defects: calamine,
oxidized penetration, flakes and thickness inhomogeneities in the
direction of the length and of the width of the strip.
[0077] The polishing is notably achieved by means of grinders or
abrasive papers. One function of the polishing is to remove the
stripping residues.
[0078] At the end of this polishing step, the initial strip 1
provided in the first step of the method according to the invention
is obtained.
[0079] Optionally, before the homogenous cold rolling step,
annealing is carried out on the strip for homogenization of the
microstructure. This microstructure homogenization annealing is
notably a continuous annealing in a heat treatment oven, called
microstructure homogenization annealing oven in the subsequent
description, with a dwelling time in the microstructure
homogenization annealing oven comprised between 2 minutes and 25
minutes and a temperature of the strip during the microstructure
homogenization annealing comprised between 850.degree. C. and
1200.degree. C.
[0080] The initial strip 1 has a constant thickness E.sub.0
comprised between 1.9 mm and 18 mm (see FIG. 1).
[0081] The initial strip 1 is then rolled during a homogenous cold
rolling step. The homogenous rolling is carried out along the
length of the initial strip 1.
[0082] By homogenous rolling, is meant a rolling which transforms a
strip having a constant thickness into a thinner strip also having
a constant thickness.
[0083] More particularly, the homogenous rolling step comprises one
or several passes performed in a mill wherein the strip passes into
a rolling gap delimited between working rolls. The thickness of
this rolling gap remains constant during each pass of the
homogenous rolling step.
[0084] This homogenous rolling step results in an intermediate
strip 3 having a constant thickness E.sub.c along the rolling
direction, i.e. along the length of the intermediate strip 3 (see
FIG. 2).
[0085] Optionally, the homogenous rolling step comprises at least
one intermediate recrystallization annealing.
[0086] When it is present, the intermediate recrystallization
annealing is carried out between two successive homogenous rolling
passes. Alternatively or optionally, it is carried out before the
flexible rolling step at the end of the homogenous rolling step,
i.e. after all the rolling passes carried out during the homogenous
rolling step.
[0087] For example, the intermediate recrystallization annealing is
a continuous annealing carried out in an intermediate annealing
oven with a temperature of the strip during the intermediate
annealing comprised between 850.degree. C. and 1200.degree. C. and
a dwelling time in the intermediate annealing oven comprised
between 30 seconds and 5 minutes.
[0088] The intermediate recrystallization annealing, or when
several intermediate recrystallization annealings are carried out,
the last intermediate recrystallization annealing of the homogenous
rolling step, is carried out when the strip has a thickness E.sub.i
comprised between the thickness E.sub.0 of the initial strip 1 and
the thickness E.sub.c of the intermediate strip 3.
[0089] When the intermediate recrystallization annealing is carried
out at the end of the homogenous rolling step, the thickness
E.sub.i of the strip during the intermediate recrystallization
annealing is equal to the thickness E.sub.c of the intermediate
strip 3 at the beginning of the flexible rolling step.
[0090] Advantageously, in the embodiment in which at least one
intermediate recrystallization annealing is carried out, a single
intermediate recrystallization annealing is carried out. In
particular, this single intermediate recrystallization annealing is
carried out between two successive homogeneous rolling passes when
the strip has a thickness E.sub.i strictly greater than the
thickness E.sub.c of the intermediate strip 3.
[0091] Preferably, the homogenous rolling step does not comprise
any intermediate annealing.
[0092] The intermediate strip 3 having a thickness E.sub.c obtained
at the end of the homogenous rolling step is then subjected to a
flexible cold rolling step.
[0093] The flexible rolling is carried out along a rolling
direction extending along the length of the intermediate strip
3.
[0094] Flexible rolling allows obtaining a strip having a variable
thickness along its length.
[0095] For this, the thickness of the rolling gap of the mill used
is continuously varied. This variation depends on the desired
thickness of the area of the strip being rolled so as to obtain a
strip having a variable thickness along its length.
[0096] More particularly, and as illustrated in FIG. 3, at the end
of the flexible rolling step a variable thickness strip 4
comprising first areas 7 having a first thickness e+s and second
areas 10 having a second thickness e, smaller than the first
thickness e+s. The first thickness e+s and the second thickness e
each correspond to a given rolling gap thickness.
[0097] The first areas 7 and the second areas 10 each have a
substantially constant thickness, e+s and e, respectively.
[0098] They are connected together through connecting areas 11
having a non-constant thickness along the length of the variable
thickness strip 4. The thickness of the connecting areas 11 varies
between e and e+s. According to an example, it varies linearly
between e and e+s.
[0099] The homogenous rolling step and the flexible rolling step
generate in the first areas 7, i.e. in the thickest areas of the
strip 4, a plastic deformation ratio .tau..sub.1, after an optional
intermediate recrystallization annealing, which is greater than or
equal to 30%, more particularly comprised between 30% and 98%,
still more particularly comprised between 30% and 80%. In the
aforementioned ranges, the plastic deformation ratio .tau..sub.1 is
advantageously greater than or equal to 35%, more particularly
greater than or equal to 40%, and still more particularly greater
than or equal to 50%.
[0100] The plastic deformation ratio .tau..sub.1 generated in the
first areas 7 is defined as follows:
[0101] If no intermediate recrystallization annealing is carried
out during the homogenous rolling step, the plastic deformation
ratio .tau..sub.1 is the total reduction ratio generated in the
first areas 7 of the strip 4 by the homogenous rolling step and the
flexible rolling step, i.e. resulting from the reduction in
thickness from the initial thickness E.sub.0 to the thickness
e+s.
[0102] In this case, the plastic deformation ratio .tau..sub.1, in
percentage, is given by the following formula:
.tau. 1 = E 0 - ( e + s ) E 0 100. ( 1 ) ##EQU00001##
[0103] Thus, in the case when no intermediate recrystallization
annealing is carried out, the plastic deformation ratio .tau..sub.1
is equal to the total reduction ratio generated in the first areas
7 by the homogenous rolling step and the flexible rolling step.
[0104] If at least one intermediate recrystallization annealing is
carried out during the homogenous rolling step, the plastic
deformation ratio .tau..sub.1 is the reduction ratio generated in
the first areas 7 by the reduction in thickness of the strip from
the thickness E.sub.i which it has during the last intermediate
recrystallization annealing carried out during the homogenous
rolling step to thickness e+s.
[0105] In this case, the plastic deformation ratio .tau..sub.1, in
percentage, is given by the following formula:
.tau. 1 = E i - ( e + s ) E i 100. ( 2 ) ##EQU00002##
[0106] Thus, in the case when one or several intermediate
annealings are carried out during the homogenous rolling step, the
plastic deformation ratio .tau..sub.1 is strictly smaller than the
total reduction ratio generated in the first areas 7 by the
homogenous rolling step and the flexible cold rolling step.
[0107] The plastic deformation ratio .tau..sub.2 after an optional
intermediate recrystallization annealing, generated in the second
areas 10, is strictly greater than the plastic deformation ratio
.tau..sub.1 in the first areas 7. It is calculated in a similar
way, by replacing e+s with e in the formulae (1) and (2) above.
[0108] The difference .DELTA..tau. of the plastic deformation ratio
between the second areas 10 and the first areas 7 is given by the
relationship .DELTA..tau.=.tau..sub.2-.tau..sub.1.
[0109] This difference .DELTA..tau. is advantageously smaller than
or equal to 13% if the thickness E.sub.0 is strictly greater than 2
mm. It is advantageously smaller than or equal to 10% if the
thickness E.sub.0 is less than or equal to 2 mm.
[0110] More particularly, the difference .DELTA..tau. is less than
or equal to 10% of E.sub.0 is strictly greater than 2 mm, and the
difference .DELTA..tau. is less than or equal to 8% if E.sub.0 is
less than or equal to 2 mm.
[0111] Advantageously, the thickness E.sub.c of the intermediate
strip 3 before the flexible rolling step is in particular equal to
the thickness e of the second areas 10 multiplied by a reduction
coefficient k comprised between 1.05 and 1.5. Advantageously, k is
equal to about 1.3.
[0112] Advantageously, the thicknesses e+s and e of the first and
second areas 7, 10 observe the equation:
e+s=(n+1).e
[0113] wherein n is a constant coefficient comprised between 0.05
and 0.5.
[0114] In other words, the first thickness e+s is equal to the
second thickness e multiplied by a multiplication coefficient
comprised between 1.05 and 1.5.
[0115] This equation can be rewritten in the following way: s=n.e,
i.e. the over-thickness s of the first areas 7 relatively to the
second areas 10 is equal to the coefficient n multiplied by the
thickness e of the second areas 10.
[0116] The thickness e of the second areas 10 is comprised between
0.05 mm and 10 mm, more particularly between 0.15 mm and 10 mm,
still more particularly between 0.25 mm and 8.5 mm. When sheets are
made, the thickness e is less than or equal to 2 mm, advantageously
comprised between 0.25 mm and 2 mm. When plates are made, the
thickness e is strictly greater than 2 mm, in particular comprised
between 2.1 mm and 10 mm, more particularly comprised between 2.1
mm and 8.5 mm.
[0117] Next the variable thickness strip 4 resulting from the
flexible rolling step is subjected to a final recrystallization
annealing.
[0118] The final recrystallization annealing is a continuous
annealing carried out in a final annealing oven. The temperature of
the final annealing oven is constant during the final
recrystallization annealing. The temperature of the strip 4 during
the final recrystallization annealing is comprised between
850.degree. C. and 1200.degree. C.
[0119] The dwelling time in the final annealing oven is comprised
between 20 seconds and 5 minutes, more particularly between 30
seconds and 3 minutes.
[0120] The running speed of the strip 4 in the final annealing oven
is constant. For example it is comprised between 2 m/min and 20
m/min for a final annealing oven with a heating length equal to 10
m.
[0121] Advantageously, the temperature of the strip 4 during the
final annealing is 1025.degree. C. In this case, the dwelling time
in the final annealing oven is for example comprised between 30
seconds and 60 seconds for a variable thickness strip 4 having
second areas 10 with a thickness e of less than or equal to 2 mm.
The dwelling time in the final annealing oven is for example
comprised between 3 minutes and 5 minutes for a variable thickness
strip 4 having second areas 10 with a thickness e strictly greater
than 2 mm.
[0122] The dwelling time in the final annealing oven, as well as
the final annealing temperature are selected so as to obtain after
the final recrystallization annealing a strip 4 having
quasi-homogenous mechanical properties and grain sizes between the
first areas 7 and the second areas 10. Subsequent description
specifies the meaning of "quasi-homogenous".
[0123] Preferably, the final annealing is carried out in a reducing
atmosphere, i.e. for example in pure hydrogen or in a
H.sub.2--N.sub.2 atmosphere. The frost temperature is preferably
less than -40.degree. C. In the case of a H.sub.2--N.sub.2
atmosphere, the content of N.sub.2 may be comprised between 0% and
95%. The atmosphere H.sub.2--N.sub.2 for example comprises
approximately 70% of H.sub.2 and 30 % of N.sub.2.
[0124] According to an embodiment, the variable thickness strip 4
continuously passes from the flexible rolling mill to the final
annealing oven, i.e. without any intermediate coiling of the
variable thickness strip 4.
[0125] Alternatively, at the end of the flexible rolling step, the
variable thickness strip 4 is coiled so as to transport it to the
final annealing oven, and then it is uncoiled and subjected to the
final recrystallization annealing.
[0126] According to this alternative, the coiled strip 4 for
example has a length comprised between 100 m and 2500 m, notably if
the thickness e of the second areas 10 of the strip 4 is
approximately 0.7 mm.
[0127] At the end of the final recrystallization annealing, a strip
4 having a variable thickness along its length is obtained having
the following characteristics.
[0128] It comprises first areas 7 having a thickness of e+s and
second areas of thickness e, optionally connected together through
connecting areas 11 with a thickness varying between e and e+s.
[0129] Preferably, the absolute value difference between the
average size of the grains of the first areas 7 and the average
size of the grains of the second areas 10 is less than or equal to
0.5 numbers according to the ASTM E112-10 standard. The average
grain size in ASTM numbers is determined by using the method of
comparison with typical images as described in the ASTM E112-10
standard. According to this method, in order to determine the
average grain size of a sample, an image of the structure of the
grains on the screen obtained by means of an optical microscope at
a given magnification of the sample having been subjected to
contrast etching is compared with typical images illustrating
twinned grains of different sizes having been subject to contrast
etching (corresponding to plate III of the standard). The average
grain size number of the sample is determined as being the number
corresponding to the magnification used borne on the typical image
which looks the most like the image seen on the screen of the
microscope.
[0130] If the image seen on the screen of the microscope is
intermediate between two successive typical images of grain sizes,
the average grain size number of the image seen in the microscope
is determined as being the arithmetic mean between the numbers
corresponding to the magnification used borne on each of the two
typical images.
[0131] More particularly, the average grain size number G1.sub.ASTM
of the first areas 7 is at most 0.5 less than the average size
number G2.sub.ASTM of the second areas 10.
[0132] The variable thickness strip 4 may have quasi-homogenous
mechanical properties.
[0133] In particular:
[0134] the absolute value difference between the yield strength at
0.2% of the first areas 7 noted as Rp1 and the yield strength at
0.2% of the second areas 10 noted as Rp2 is less than or equal to 6
MPa, and
[0135] the absolute value difference between the ultimate tensile
strength of the first areas 7 noted as Rm1 and the ultimate tensile
strength of the second areas 10 noted as Rm2 is less than or equal
to 6 MPa.
[0136] By yield strength at 0.2%, is conventionally meant the
stress value at a plastic deformation of 0.2%.
[0137] Conventionally, the ultimate tensile strength corresponds to
the maximum stress before striction of the test sample.
[0138] In the illustrated example, the variable thickness strip 4
has a pattern periodically repeated over the whole length of the
strip 4. This pattern successively comprises one half of a first
area 7 with a length
L 1 2 , ##EQU00003##
a connecting area 11 of length L3, a second area 10 of length L2, a
connecting area 11 of length L3 and one half of a first area 7 with
a length of
L 1 2 . ##EQU00004##
[0139] Advantageously, the length L2 of the second area 10 is
substantially greater than the length L1 of the first area 7. As an
example, the length L2 is comprised between 20 and 100 times the
length L1.
[0140] Each sequence formed by a first area 7 surrounded by two
connecting areas 11 forms an over-thickness area of the variable
thickness strip 4, i.e. an area with a thickness greater than e.
Thus, the variable thickness strip 4 comprises second areas 10 of
length L2 with a thickness e, separated between them by
over-thickness areas.
[0141] After the final recrystallization annealing, the variable
thickness strip 4 is cut out in the over-thickness areas,
preferably in the middle of the over-thickness areas.
[0142] Blanks 12 illustrated in FIG. 4 are thereby obtained,
comprising a second area of length L2 surrounded at each of its
longitudinal ends by a connecting area 11 of length L3 and by a
half of a first area 7 of length
L 1 2 . ##EQU00005##
[0143] At the end of the cutting step, the blanks 12 are leveled
according to a known leveling method.
[0144] The blanks 12 are then wound into unit coils.
[0145] According to an alternative of the manufacturing method
described above, the leveling of the variable thickness strip 4 is
carried out after the final recrystallization annealing and before
the cutting out of the blanks 12.
[0146] According to this alternative, the leveled variable
thickness strip 4 is cut out in the over-thickness areas in order
to form the blanks 12. Preferably, the strip 4 is cut out in the
middle of the over-thickness areas.
[0147] The cutting out is for example performed on the leveler used
for leveling the strip 4. Alternatively, the leveled strip 4 is
wound into a coil, and then cut out on a machine different from the
leveler.
[0148] The blanks 12 are then wound as unit coils.
[0149] By means of the manufacturing method described above, blanks
12 formed in one piece comprising a central area 13 of thickness e,
surrounded by reinforced ends 14, i.e. with a thickness greater
than the thickness e of the central area 13, are obtained. The ends
14 correspond to over-thickness areas of the variable thickness
strip 4 and the central area 13 corresponds to a second area 10 of
the variable thickness strip 4 from which the blank 12 has been cut
out.
[0150] These blanks 12, which have a variable thickness along their
length while being formed with one part, do not have the weaknesses
of the welded assemblies of the state of the art. Further, their
reinforced ends 14 allow assembling them by welding with other
parts while minimizing the mechanical weaknesses due to this
assembling by welding.
[0151] According to alternatives, the blanks 12 may for example be
obtained by cutting out the strip 4 at other locations than in two
successive over-thickness areas. For example, they may be obtained
by alternately cutting them in an over-thickness area and in a
second area 10. In this case, blanks 12 are obtained having a
single reinforced end 14 with a thickness greater than e.
[0152] They may also be obtained by cutting out in two successive
second areas 10.
[0153] As an example, and as illustrated in FIG. 5, a blank 12
according to the invention may be assembled with a second part 16
by welding one of the reinforced ends 14 of the blank 12 to an edge
of the second part 16. The thickness of the second part 16 is
preferably greater than the thickness of the central area 13 of the
blank 12. The weld performed is more particularly a lap weld.
[0154] The part 16 may be a blank 12 as described above.
[0155] Thus, in FIG. 6, two blanks 12 assembled end to end by
welding are illustrated. These two blanks 12 are welded together
through their reinforced ends 14.
[0156] In the examples illustrated in FIGS. 5 and 6:
[0157] the length of the central area 13 is for example comprised
between 40 m and 60 m; and
[0158] the length of each reinforced end 14 is for example
comprised between 0.5 m and 2 m.
[0159] The second thickness e is notably about equal to 0.7 mm.
[0160] The first thickness e+s is about equal to 0.9 mm.
[0161] Alternatively, a non-planar part is formed from the blank
12.
[0162] Thus, in the example illustrated in FIG. 7, a tube segment
18 is formed from the blank 12.
[0163] The edges of the blank 12 extending along the length of the
blank 12 are called longitudinal edges.
[0164] In order to manufacture the tube segment 18, the blank 12 is
rolled up along its width, i.e. around a longitudinal axis L so as
to form a rolled up blank 12. The longitudinal edges of the rolled
up blank 12 are then welded together so as to form the tube segment
18. This tube segment 18 has a cylindrical central area 20 of
thickness e and cylindrical reinforced ends 22 with a thickness
greater than the thickness e, and in particular equal to e+s.
[0165] A tube 24 is then made by welding at least two tube segments
18 together through their reinforced ends 22. The weld is an
orbital weld, in particular a weld of the end-to-end type.
[0166] The thickness e+s of the reinforced ends 22 is defined
depending on the traction forces which the tube 24 has to undergo
during its mounting and during its use.
[0167] Such a tube 24 is for example a cryogenic tube suitable for
conveying liquefied natural gas and intended to form for example
the main tube coated with a material protecting it against the
corrosion of a cryogenic under-water conduit for conveying
liquefied natural gas or the inner tube of such a conduit.
[0168] In this case, for example:
[0169] the thickness e is equal to about 8.2 mm;
[0170] the thickness e+s is equal to about 9.43 mm.
[0171] The length L2 of the central area 20 of a tube segment 18 is
equal to about 8 m.
[0172] The manufacturing method according to the invention is
particularly advantageous. Indeed, it allows obtaining a strip made
of an alloy mainly based on iron and nickel having the chemical
composition defined above having areas with different thicknesses
but quasi-homogeneous mechanical properties. These properties are
obtained by the use of a plastic deformation ratio after an
optional intermediate recrystallization annealing generated by the
homogenous rolling and flexible rolling steps in the thickest areas
greater than or equal to 30%.
[0173] The following experimental examples illustrate the
significance of the range of plastic deformation ratio claimed for
this type of alloy.
[0174] In a first series of experiments, variable thickness sheets
were made, i.e. variable thickness strips 4 having a thickness e of
the second areas 10 is less than or equal to 2 mm.
[0175] Table 1 hereafter illustrates tests for manufacturing sheets
having variable thickness without any intermediate
recrystallization annealing.
[0176] Table 2 hereafter contains characteristics of the sheets
obtained by the tests of Table 1.
[0177] Table 3 hereafter illustrates tests for manufacturing sheets
with variable thickness with an intermediate recrystallization
annealing at thickness E.sub.i.
[0178] Table 4 hereafter contains characteristics of the sheets
obtained by the tests of Table 3.
[0179] In a second series of experiments, variable thickness plates
were manufactured, i.e. variable thickness strips 4 having a
thickness e of the second areas 10 is strictly greater than 2
mm.
[0180] Table 5 illustrates tests for manufacturing variable
thickness plates with or without any intermediate annealing.
[0181] Table 6 hereafter contains characteristics of the plates
obtained by the tests of Table 5.
[0182] In all the tables, the tests according to the invention are
underlined.
[0183] It is seen that when the plastic deformation ratio
.tau..sub.1 after an optional intermediate recrystallization
annealing is greater than or equal to 30% (tests 1 to 7 of Table 1,
1 to 3 of Table 3 and 1 to 9 of Table 5), the obtained variable
thickness strip 4 has an average grain size difference between the
average size of the grains of the first areas 7 (thickness e+s) and
the size of the grains of the second areas 10 (thickness e) of less
than or equal to 0.5 ASTM numbers in absolute value. This small
average grain size difference between the first areas 7 and the
second areas 10 results in quasi-homogenous mechanical properties,
i.e. a difference in yield strength at 0.2%, DeltaRp between the
first areas 7 and the second areas 10 of less than or equal to 6
MPa in absolute value, and a difference between the ultimate
tensile strength DeltaRm of the first areas 7 and of the second
areas 10 of less than or equal to 6 MPa in absolute value.
[0184] It is thus possible to obtain a variable thickness strip 4,
having quasi-homogenous mechanical properties and grain sizes at
the end of a very simple recrystallization annealing, since it is
carried out at a constant temperature and constant running
speed.
TABLE-US-00001 TABLE 1 Wavelength E.sub.0 E.sub.c e e + s L1 L2 L3
.tau.1 .tau.2 .tau.2 - .tau.1 Final annealing Test (m) (mm) k (mm)
(mm) n = s/e (mm) (m) (m) (m) (%) (%) (%) T.degree. C.; duration 1
50 4.2 1.3 2.0 1.5 0.25 1.88 1.50 1.90 44.7 55 64 9 1025.degree.
C.; 60 s 2 50 4.2 1.15 1.7 1.5 0.15 1.73 1.50 1.90 44.7 59 64 5
1025.degree. C.; 60 s 3 50 3.2 1.15 1.2 1.0 0.15 1.15 1.00 1.50
46.0 64 69 5 1025.degree. C.; 60 s 4 50 2.6 1.3 0.9 0.7 0.25 0.88
1.00 1.50 46.0 66 73 7 1025.degree. C.; 40 s 5 50 2.6 1.15 0.8 0.7
0.15 0.81 1.00 1.50 46.0 69 73 4 1025.degree. C.; 40 s 6 60 2.6 1.3
0.9 0.7 0.15 0.81 1.00 1.50 56.0 69 73 4 1025.degree. C.; 40 s 7 50
2.1 1.3 0.7 0.5 0.15 0.58 1.20 1.50 45.8 73 76 4 1025.degree. C.;
30 s 8 50 2.3 1.3 2.3 1.8 0.25 2.25 1.20 1.50 45.8 2 22 20
1025.degree. C.; 60 s
TABLE-US-00002 TABLE 2 Properties at thickness e + s Properties at
thickness e Rp Rm Rp Rm Delta Rp Delta Rm Test G1.sub.ASTM (MPa)
(MPa) G2.sub.ASTM (MPa) (MPa) (MPa) (MPa) DeltaG.sub.ASTM 1 8 288
487 8.5 292 491 -4 -4 0.5 2 8.5 293 492 9 296 495 -3 -3 0.5 3 8.5
293 492 9 295 495 -2 -3 0.5 4 8.5 293 490 9 296 496 -3 -6 0.5 5 9
297 496 9 296 496 1 0 0 6 9 297 495 9 296 496 1 -1 0 7 9.5 300 501
9.5 300 501 0 0 0 8 7.5 284 482 8.5 292 490 -8 -8 1
TABLE-US-00003 TABLE 3 Wave- Annealing at length E.sub.0 E.sub.i
E.sub.i E.sub.c e e + s L1 L2 L3 .tau.1 .tau.2 .tau.2 - .tau.1
Final annealing Test (m) (mm) k (mm) T.degree. C.; duree (mm) (mm)
n = s/e (mm) (m) (m) (m) (%) (%) (%) T.degree. C.; duration 1 50
2.6 1.3 1.5 1025.degree. C.; 50 s 0.8 0.6 0.25 0.75 1.20 1.50 45.8
50 60 10 1025.degree. C.; 40 s 2 50 2.6 1.3 1.5 1025.degree. C.; 50
s 0.8 0.6 0.15 0.69 1.20 1.50 45.8 54 60 6 1025.degree. C.; 40 s 3
60 2.6 1.3 1.5 1025.degree. C.; 50 s 0.7 0.5 0.15 0.58 1.20 1.50
55.8 62 67 5 1025.degree. C.; 30 s 4 50 4.2 1.30 2.00 1025.degree.
C.; 80 s 1.95 1.5 0.25 1.88 1.50 1.90 44.7 6 25 19 1025.degree. C.;
60 s 5 50 4.2 1.15 2.00 1025.degree. C.; 80 s 1.73 1.5 0.15 1.73
1.50 1.90 44.7 14 25 11 1025.degree. C.; 60 s 6 50 3.2 1.30 1.30
1025.degree. C.; 50 s 1.30 1.0 0.25 1.25 1.50 1.90 44.7 4 23 19
1025.degree. C.; 60 s 7 50 3.2 1.15 1.50 1025.degree. C.; 60 s 1.15
1.0 0.15 1.15 1.00 1.50 46.0 23 33 10 1025.degree. C.; 60 s 8 60
2.6 1.15 1.00 1000.degree. C.; 40 s 0.81 0.7 0.15 0.81 1.00 1.50
56.0 20 30 11 1025.degree. C.; 40 s
TABLE-US-00004 TABLE 4 Properties at thickness e + s Properties at
thickness e Rp Rm Rp Rm Delta Rp Delta Rm Test G1.sub.ASTM (MPa)
(MPa) G2.sub.ASTM (MPa) (MPa) (MPa) (MPa) DeltaG.sub.ASTM 1 8.5 292
491 8.5 293 491 -1 0 0 2 8.5 293 492 8.5 291 492 2 0 0 3 8.5 293
490 9 296 496 -3 -6 0.5 4 7 281 478 8 290 487 -9 -9 1 5 7 281 477 8
288 487 -7 -10 1 6 6.5 277 473 8 288 487 -11 -14 1.5 7 7 282 477 8
289 487 -7 -10 1 8 6.5 277 474 7.5 285 482 -8 -8 1 9 7 282 479 8
289 487 -7 -8 1
TABLE-US-00005 TABLE 5 Wave- Annealing at .tau.2 - length E.sub.0
E.sub.i E.sub.i E.sub.c e e + s L1 L2 L3 .tau.1 .tau.2 .tau.1 Final
annealing Test (m) (mm) k (mm) T.degree. C.; duration (mm) (mm) n =
s/e (mm) (m) (m) (m) (%) (%) (%) T.degree. C.; duration 1 12 16
1.30 Neant 10.7 8.2 0.25 10.25 1.00 1.50 8.0 36 49 13 1025.degree.
C.; 5 min 2 6 16 1.15 Neant 9.4 8.2 0.15 9.43 0.50 0.75 4.0 41 49 8
1025.degree. C.; 5 min 3 12 8.2 1.30 Neant 5.5 4.2 0.25 5.25 0.50
0.75 10.0 36 49 13 1025.degree. C.; 3 min 4 12 8.2 1.15 Neant 4.8
4.2 0.15 4.83 1.50 2.25 6.0 41 49 8 1025.degree. C.; 3 min 5 6 8.2
1.30 Neant 4.2 3.2 0.25 4.00 0.80 1.20 2.8 51 61 10 1025.degree.
C.; 3 min 6 9 8.2 1.15 Neant 3.7 3.2 0.15 3.68 1.00 1.50 5.0 55 61
6 1025.degree. C.; 3 min 7 12 16 1.30 8.2 1050.degree. C.; 5 min
4.2 3.2 0.25 4.00 1.00 1.50 8.0 51 61 10 1025.degree. C.; 3 min 8
12 16 1.15 8.2 1050.degree. C.; 5 min 4.8 4.2 0.15 4.83 0.50 0.75
10.0 41 49 8 1025.degree. C.; 3 min 9 6 16 1.15 8.2 1050.degree.
C.; 5 min 3.7 3.2 0.15 3.68 0.50 0.75 4.0 55 61 6 1025.degree. C.;
3 min
TABLE-US-00006 TABLE 6 Properties at thickness e + s Properties at
thickness e Test G1.sub.ASTM Rp (MPa) Rm (MPa) G2.sub.ASTM Rp (MPa)
Rm (MPa) Delta Rp (MPa) Delta Rm(MPa) DeltaG.sub.ASTM 1 7 280 479
7.5 285 483 -5 -4 0.5 2 7 281 477 7.5 285 483 -4 -6 0.5 3 7.5 285
482 8 288 487 -3 -5 0.5 4 8 288 487 8 288 487 0 0 0 5 8.5 293 492
8.5 292 492 1 0 0 6 8.5 292 491 9 297 496 -5 -5 0.5 7 8.5 291 490
8.5 293 490 -2 0 0 8 8 289 487 8.5 292 491 -3 -4 0.5 9 8.5 292 491
8.5 292 490 0 1 0
* * * * *